Boat with improved stringer and method of manufacturing same

ABSTRACT

A boat with an improved stringer, and a method of manufacturing same, according to which a first stringer portion is fabricated from a relatively low-strength material, and a second stringer portion is fabricated from a relatively high-strength material, and the stringer portions are mounted in a hull.

BACKGROUND

This invention relates to a boat having a stringer for providing stiffening for the boat hull and support for a floor and a motor.

A conventional manufacturing technique used by boat manufacturers, especially in the manufacture of boats having hulls of glass fiber-reinforced resin, is to employ a stringer, often constructed of a low-density foam, which provides a relatively inexpensive way to form the structural framing of the boat and to both stiffen the molded hull of the boat and provide support for the floor of the boat. However, the low-density foam is often not strong enough to adequately mount a relatively heavy motor in the hull.

This invention is directed to a stringer for a boat hull which eliminates this problem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a stringer according to an embodiment of the invention.

FIG. 2 is an isometric view of the stringer of FIG. 1, mounted in a boat hull.

FIG. 3 is a partial sectional view taken along the lines 3-3, respectively, of FIG. 1.

FIG. 4 is an enlarged view of a portion of the components of FIG. 3.

DETAILED DESCRIPTION

Referring to FIG. 1 of the drawings the reference numeral 10 refers, in general, to a stringer according to an embodiment of the invention. The stringer 10 consists of an integral, unitary structure 10 a formed by two spaced parallel beams 12 and 14, having three spaced cross pieces 16 a and 16 b, 18 a and 18 b, and 20 a and 20 b, respectively, formed integrally therewith and extending outwardly from their respective outer side surfaces. The transverse lengths of the cross pieces 16, 18, and 20 increase in a longitudinal direction along the beams 12 and 14 from the nose 22 to the other corresponding ends of the beams. A tapered nose 22 extends across corresponding ends of the beams 12 and 14 and is formed integrally therewith. The inner surfaces of the other end portions of the beams 12 and 14 are stepped to form notches 12 a and 14 a, respectively.

The structure 10 a is fabricated from a relatively inexpensive, and therefore a relatively low-strength, material such as a relatively low-density foam. For example, the foam material can be in the form of a polyurethane foam that is injected into a mold so that the foam expands to fill the mold and, when cured, forms the integral, unitary structure.

The stringer 10 also includes two longitudinal struts 22 a and 22 b that extend from the latter ends of the beams 12 and 14, respectively, and two transverse struts 24 a and 24 b extending outwardly from the struts 22 a and 22 b, respectively. The struts 22 a, 22 b are fabricated from a relatively high-strength material that is stronger than the material of the structure 10 a so that the struts can support a motor for the boat 10 in a manner to be described. An example of this high-strength material is a compressed, relatively high-density, foam, such as polyurethane, impregnated with fiberglass stands and\or one or more fiberglass mats to increase its density and strength. The struts 24 a and 24 b can be fabricated from the same material as the struts 22 a and 22 b.

One end portion of the strut 22 a extends in the notch 12 a, and one end portion of the strut 22 b extends in the notch 14 a, and the struts are secured in these positions in any conventional manner, such as by using a bonding agent in the manner discussed above. The struts 24 a and 24 b are secured to the struts 22 a and 22 b, respectively, in any conventional manner.

FIG. 2 depicts the stringer 10 installed in a boat hull 30 which is formed of a glass fiber-reinforced resin. The longitudinal axis of the stringer 10 coincides with the longitudinal axis of the hull 30 and the nose 22 of the stringer is positioned in the front portion of the hull 30. The above-mentioned varying lengths of the cross pieces 16, 18, and 20 are such that their respective ends engage the corresponding side walls of the hull 30. The struts 22 a and 22 b extend to, or near, the rear end of the hull 30, and the struts 24 a and 24 b extend towards the respective sides of the hull 30 with their respective ends engaging the inner wall of the hull. It is understood that the lower surfaces of the stringer 10 are contoured to conform or fit with the corresponding contoured surfaces of the hull 30.

After the stringer 10 is positioned in place in the hull 30 as shown in FIG. 2, one or more layers of a bonding agent, such as a reinforced putty, is applied at the seams between the lower surface of the stringer and the corresponding upper surface of the hull to effectively bond the stringer 10 in place in the hull. Then, a fiberglass cloth is placed over the upper and side surfaces of the stringer 10, including the structure 10 a and the struts 22 a, 22 b, 24 a and 24 b, after which a resin, along with a suitable catalyst, is sprayed over the cloth so that it seeps through the cloth to the stringer 10. After curing, the stringer 10 is effectively bonded to the hull 30.

Also, the hull 30 and at least the structure 10 a of the stringer 10 can be molded in the manner discussed above, and the stringer 10 placed in the hull 30 before the stringer and the hull are completely cured, which allows a chemical bonding between the contacting surfaces of the stringer and the hull. This latter technique can be in addition to, or in place of, the application of the bonding agent described above. If only the structure 10 a of the stringer 10 is bonded to the hull 30 in the above manner then the struts 22 a, 22 b, 24 a and 24 c can be bonded to the stringer 10 by the bonding agent as discussed above. Then the fiberglass cloth and the resin would be applied as discussed above.

The structure 10 forms the structural framing of the boat and stiffens the hull 30 while, as stated above, the material forming the struts 22 a and 22 b is strong enough to support a motor (not shown) for the boat 10.

An example of a technique for mounting a motor to the inner vertical surfaces of the struts 22 a and 22 b is shown in FIG. 3. In particular, two generally U-shaped saddles, or cradles, 32 a and 32 b are placed over the struts 22 a and 22 b, respectively, adjacent the rear ends of the notches 12 a and 14 a, respectively, and are secured to the struts in any conventional manner, such as by a bonding agent in the manner discussed above. The saddles 32 a and 32 b extend longitudinally from the end of the notches 12 a and 14 a, respectively, towards the rear end of the hull 30 for a relatively short distance, and are fabricated from a relatively strong material, such as aluminum, to provide structural integrity for mounting the motor.

Two mounting brackets 34 a and 34 b are mounted to the inner vertical walls of the saddles 32 a and 32 b, respectively, in a manner better shown in FIG. 4 in connection with the mounting bracket 34 a. In particular, a bolt 36 extends through aligned openings in the bracket 34 a, the saddle 32 a and the strut 22 a and receives a nut 38 to secure the bracket. It is understood that the bracket 34 b is mounted to the strut 22 b in the same manner. In their mounted positions, a leg of each bracket 34 a and 34 b defines a horizontally extending mounted surface for receiving the motor, or a mount for a motor, that extends in the space between the brackets.

The stringer 10 defines an essentially planer upper surface for receiving a floor (not shown) which can be installed over at least a portion of the stringer 10 while defining a space in the hull 30 for housing the motor. The floor can be constructed of wood, or other suitable material, and can be fastened to the planar upper surface of the stringer 10 in any conventional manner. Also, the surfaces of the floor contacting the corresponding inner side surfaces of the hull 30 can be secured to the latter surfaces in any convention manner.

Although the stringer 10 provides significant flotation for the boat, it is understood that, before the floor is mounted in the above manner, additional flotation may be added to the boat by injecting an expandable foam into one or more of the spaces between the beams 12 and 14, the cross pieces 16 a, 16 b, 18 a, 18 b, 20 a, and 20 b, and the corresponding surfaces of the hull 30.

Variations and Alternatives

1. A broad concept of this invention is the use of a relatively inexpensive, low-strength material that forms a portion of the stringer 10 to both stiffen the molded hull of the boat and provide support for the floor of the boat, and the use of a relatively high-strength material that supports the motor. Therefore, the invention is not limited to the specific materials (low and high-density foam) discussed above for the purpose of example only, but rather is equally applicable to other materials consistent with the above.

2. The struts 22 a and 22 b and/or the struts 24 a and 24 b are not necessarily part of the stringer 10 but can be separate from the stringer.

3. The struts 24 a and 24 b do not necessarily have to be fabricated from the same material as the struts 22 a and 22 b but rather can be fabricated from another material.

4. The stringer 10 may be adapted to any configuration of boat hull.

5. The motor mounting technique discussed above is merely one non-limitive example and other techniques can be utilized within the scope of the invention.

7. One or both of the mounting brackets 34 a and 34 b may be mounted on only one of the struts or on both of the struts 22 a and 22 b.

8. Additional mounting brackets, identical to the mounting brackets 34 a and 34 b, may be mounted on one or both of the struts 22 a and 22 b.

9. The saddles 36 a and 36 b can be eliminated in which case the mounting brackets 38 a and 38 b would be mounted directly to the vertical walls of the struts 22 a and 22 b, respectively.

10. The composition of the bonding agent discussed above may be varied, and, for example, a glass fiber-reinforced resin may be used as a bonding agent instead of, or in addition to, the reinforced putty.

11. Spatial references, such as “horizontal”, “vertical”, “front”, “rear”, etc. are for the purpose of illustration only and do not limit the specific orientation or location of the structure described above.

Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many other modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. 

1. A boat comprising: a hull; and a stringer disposed in the hull and comprising: a first portion formed by a relatively low-strength material; and a second portion formed by a relatively high-strength material.
 2. The boat of claim 1 wherein the high-strength material is sufficient to support a motor.
 3. The boat of claim 1 wherein the first stringer portion forms the structural framing of the boat and stiffens the hull.
 4. The boat of claim 1 wherein the second stringer portion is bonded to the first stringer portion.
 5. The boat of claim 1 wherein the first and second stringer portions are bonded to the hull.
 6. The boat of claim 1 wherein the low-strength material is a relatively low-density polyurethane foam and the high-strength material is a relatively high-density polyurethane foam.
 7. The boat of claim 6 wherein the high-density foam is impregnated with fiberglass.
 8. The boat of claim 1 further comprising a fiberglass cloth extending over the first and second stringer portions.
 9. The boat of claim 8 further comprising a resin extending through the fiberglass cloth and to the stringer portions to bond the fiberglass to the portions.
 10. The boat of claim 1 wherein the first stringer portion comprises at least two spaced parallel beams, a nose disposed at the corresponding ends of the beams, and at least one cross piece extending from the beams.
 11. A method of manufacturing a boat, the method comprising: fabricating a first stringer portion of a relatively low-strength material; fabricating a second stringer portion of a relatively high-strength material; and mounting the stringer portions in a hull.
 12. The method of claim 11 further comprising supporting a motor on the second stringer portion.
 13. The method of claim 11 wherein the first stringer portion forms the structural framing of the boat and stiffens the hull.
 14. The method of claim 11 further comprising bonding the second stringer portion to the first stringer portion.
 15. The method of claim 11 further comprising bonding the first and second stringer portions to the hull.
 16. The method of claim 11 wherein the low-strength material is a relatively low-density polyurethane foam and the high-strength material is a relatively high-density polyurethane foam.
 17. The method of claim 16 further comprising impregnating the high-density foam with fiberglass.
 18. The method of claim 11 further comprising disposing a fiberglass cloth over the first and second stringer portions.
 19. The method of claim 18 further comprising applying a resin to the fiberglass cloth and to the stringer portions to bond the fiberglass to the portions.
 20. A method of manufacturing a boat, comprising: molding a hull of a plastic material. molding a stringer of a plastic material, placing the stringer in the hull; and then allowing the stringer and the mold to cure to bond the stringer to the mold.
 21. The method of claim 20 wherein the hull is of a glass fiber-reinforced resin and the stringer is a polyurethane foam.
 22. The method of claim 21 wherein one portion of the stringer is a relatively low-density foam and another portion of the stringer is of a relatively high-density foam.
 23. The method of claim 22 further comprising mounting a motor to the other portion of the stringer.
 24. The method of claim 22 further comprising bonding the other portion of the stringer to the one portion of the stringer.
 25. A method of manufacturing a boat, comprising: forming a unitary stringer of a relatively low-strength material; providing at least one strut of a relatively high-strength material; bonding the at least one strut to the stringer, bonding the stringer and the strut to a hull, and supporting a motor on the strut.
 26. The method of claim 25 wherein the low-strength material is a low-density polyurethane foam, and wherein the high-strength material is a relatively high-density polyurethane foam.
 27. The method of claim 26 further comprising impregnating the high-density foam with fiberglass.
 28. The method of claim 25 wherein the hull is molded from a glass fiber-reinforced resin and wherein the stringer is bonded to the hull by placing the stringer in contact with the hull after the stringer and the hull have been molded and before they have been completely cured, to chemically bond the stringer to the hull. 